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3.5.7Exchange and Transport

Cardiovascular Disease Data — AQA A Level Biology 7402 Revision Notes & Topical Questions

5 min read 9 parts Lesson 38 of 48 1 quiz

📚 AQA A Level Biology 7402 Hub / Topical Revision
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Lesson summary

3.5.7 Cardiovascular Disease Data — AQA A Level Biology 7402 notes: Explain how atheroma, thrombosis and other factors lead to cardiovascular disease and interpret data on risk factors.Cardiovascular disease (CVD) includes coronary heart disease (CHD), stroke and heart failure.

  • atherosclerosis
  • coronary arteries
  • myocardial infarction
  • Exam-style question 1
  • Exam-style question 2
  • Exam-style question 3

Section 1 of 9Atheroma and atherosclerosis

Cardiovascular disease (CVD) includes coronary heart disease (CHD), stroke and heart failure. A common cause is the formation of atheroma in artery walls:

Damage to the endothelium of an artery, for example by high blood pressure, toxins from smoking or high blood glucose, allows an inflammatory response.
White blood cells (monocytes becoming macrophages) enter the wall and take up cholesterol from low-density lipoprotein (LDL), forming foam cells.
A fatty plaque of cholesterol, dead cells and fibrous tissue builds up under the endothelium, called an atheroma.
Atherosclerosis
The wall loses its elasticity and hardens (atherosclerosis) and the lumen narrows, increasing blood pressure and reducing blood flow.

Section 2 of 9Thrombosis, angina and infarction

If the plaque ruptures the endothelium, platelets are exposed to collagen, and a blood clot (thrombus) forms, involving thrombin converting soluble fibrinogen to insoluble fibrin.

The clot may block the artery completely.
Coronary arteries
In the coronary arteries, a partial blockage causes angina (chest pain on exertion) and a complete blockage causes a myocardial infarction (heart attack),
  • because the heart muscle receives no oxygen and glucose and cannot respire aerobically,
  • so cells die.
Stroke
In an artery supplying the brain, the result is a stroke.
A clot that breaks loose and travels is an embolus.

Section 3 of 9Risk factors

Risk factorHow it raises risk
High blood pressureDamages endothelium; makes plaques more likely to rupture
SmokingCarbon monoxide and other chemicals damage endothelium; nicotine raises blood pressure and heart rate; reduces oxygen carriage
High blood cholesterol (LDL)Cholesterol builds up in atheroma
Diet high in saturated fat and saltRaises LDL and blood pressure
Inactivity, obesity, diabetesIncrease blood lipids, pressure and damage
Genetics, age, sexCannot be changed; family history raises risk

High-density lipoprotein (HDL) carries cholesterol back to the liver and is protective.

Section 4 of 9Interpreting data

1
Describe patterns with figures, such as "the death rate from CHD in group A is 3 times higher than in group B".
2
Use per-population rates (for example per 100 000) to compare groups of different sizes.
3
Look for dose-response: risk rising with cholesterol level or the number of cigarettes smoked.
4
Discuss confounding variables, such as the way smokers also may eat poorly, and distinguish correlation from causation (3.2.10).
5
Evaluate how large and representative the study group is, and how long it lasted.

Example calculationif the death rate was 320 per 100 000 in 2000 and 240 per 100 000 in 2020, the percentage decrease = (320 − 240) ÷ 320 × 100 = 25%.

Section 5 of 9Prevention and treatment

Lifestyle changesstopping smoking, reducing saturated fat and salt, regular exercise, weight control.

Statins
Drugs: statins reduce LDL cholesterol; antihypertensives (for example beta blockers, ACE inhibitors and diuretics) lower blood pressure; anticoagulants (warfarin) and antiplatelet drugs (aspirin) reduce clotting.
Surgery includes angioplasty with a stent, and bypass grafts.
Each treatment has benefits and risks, and decisions weigh these against the patient's overall risk.

Section 6 of 9Worked data example

A study followed 10 000 people for 10 years.

Worked data example
Of those with a blood cholesterol below 5 mmol dm−3, 150 had a heart attack; of those with levels above 7 mmol dm−3, 480 had a heart attack, out of 6000 and 4000 people in each group respectively.
The incidence is 150 ÷ 6000 = 2.5% in the low group and 480 ÷ 4000 = 12% in the high group, so the relative risk is 12 ÷ 2.5 = 4.8.

A good conclusion would state that there is a positive correlation between the cholesterol level and the incidence of heart attacks, that the risk is nearly five times greater in the high group, and that the data support a link but do not prove cause, as people with a high cholesterol level may also smoke, have a poorer diet or inherit other risk factors. A mechanism (cholesterol incorporated in atheroma) and trials in which lowering cholesterol with statins reduces events strengthen the case for cause.

Remember that cardiovascular disease is a leading cause of death worldwide, and that most risk factors are linked to lifestyle. Public health measures include food labelling, taxation, education and smoking bans; evaluate them by asking whether the trend in the incidence of the disease changes over time after the measure is introduced.

Section 7 of 9Exam-style questions

  1. Describe how atheroma can lead to a myocardial infarction. [4]4 marks

  2. Death rates from CHD per 100 000 were 450 in smokers and 150 in non-smokers. Calculate how many times greater the risk is in smokers and give one reason why this does not prove smoking causes CHD. [3]3 marks

  3. Explain how statins reduce the risk of CHD. [2]2 marks

Section 8 of 9Key terms

TermMeaning
AtheromaFatty deposit in the wall of an artery.
AtherosclerosisHardening and narrowing of arteries by atheroma.
ThrombusBlood clot formed within a vessel.
Myocardial infarctionDeath of heart muscle due to a blocked coronary artery.
LDLLow-density lipoprotein that carries cholesterol to tissues.
StatinDrug that lowers blood cholesterol.

Section 9 of 9Exam technique

1
Saying that cholesterol is always harmful; HDL is protective.
2
Confusing atheroma (plaque) with thrombosis (clot).
3
Stating that a heart attack is caused by a blockage in the vein.
4
Not linking low oxygen supply to cell death in a heart attack.
5
Drawing a causal conclusion from a single correlation.

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